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What is Food Allergies?
Food Allergy – Introduction and Causes

Food allergies are negative reactions of the human body to allergens present in the consumed products. In normal circumstances, the body has the ability to digest all food items that are necessary for survival. However in some cases, the immune system mistakenly perceives the constituents as harmful antigens that pose a threat to proper functioning of normal bodily functions. In such instances, the immune system attacks the false antigens and consequently causes reactions that manifest themselves in various ways including food allergies.

The most well known type of food allergy is Type I mediated by Immunoglobulin E (IgE). This type shows immediate reactions within a few seconds to up to half an hour. The symptoms can be mild or severe and in some cases life threatening. Medical experts suggest that people suffering from the ailment

should always keep an epinephrine shot handy with them for self-treatment in case of emergencies. The Gell–Coombs classification of hypersensitivity reactions also adds Immunoglobulin G (IgG) mediated responses as allergic reactions (Type III). However, these reactions happen over a period of time from a few hours to a few days after the food is ingested. As such, though the immunological perspective does tend them to be classified as allergic reactions, the medical viewpoint sometimes differs. There are quite a few discussions to be found on the subject with vocal proponents of each view stressing the correctness of their opinions through case studies and research papers.

Food Allergy – Types

There are three primary varieties of food allergies with each type having its own type of antibodies and pathological pathways

  • Acute Symptomatic Type I
  • Asymptomatic Type I
  • Delayed Allergy Type III
Acute Symptomatic Type I

Generally referred to as classic Type I food allergy, the condition is characterised by a near-immediate display of symptoms after food ingestion. The IgE mediated situation may also result in anaphylaxis, a severe allergic reaction that causes itchiness, rashes, swelling of the throat and low blood pressure. In this case, IgE binds itself to mastocytes and releases inflammatory cell-derived mediators such as histamines and cytokines. As histamine is a strong vasodilatator, it causes skin irritations and itching, inflammation of the mucosa and substantial fall in blood pressure. An epinephrine shot should be kept handy by all people suffering from the condition. Immediate intensive care is required in severe cases.

Asymptomatic Type I

This allergy is caused by the presence of the IgG4 antibody that is unable to bring about an inflammatory reaction. The issue occurs when the body builds up IgG4 levels instead of IgE due to genetics and other physiological factors. The antibody has only about 1% capacity of IgE to release cell-derived mediators such as histamines. As such, there is a general lack of symptoms and individuals are unable to realise that they are suffering from the problem due to lack of noticeable adverse reactions. Though considered to be mostly harmless, a desensitization therapy of an IgE mediated allergy helps increase the number of IgG4. The condition may remain asymptomatic or may start displaying symptoms based on the ratio between Ig4 and IgE.

Delayed Allergy Type III

As the name suggests, Type III allergies manifest symptoms hours or even days after the ingestion of food. The symptoms are different from those that characterise Type I allergies. As the condition does not result in acute problems that characterise Type I symptomatic issues, people tend to ignore the problem for long periods of time. Individuals are also unable to directly correlate what they ate hours or days previously with the problem. This consequently results in chronic ailments that take time to manifest themselves. The problem is mediated by IgG, especially IgG1 and IgG3. The antibodies set off a series of reactive proteins that interact with the consumed products and cause phagocytosis.

Both IgG1 and IgG3 fix the antigen which leads to the formation of circulating immune complexes that are normally degraded by macrophages in the liver. However, as the circulating immune complexes are fixed on a sensitized tissue, the break-up takes place locally. A regular occurrence of this on the sensitized tissue damages the cells and causes various complications. These complications manifest themselves through varied symptoms depending on the area affected. The pathological pathway includes neutrophils and oxidative stress and not eosinophyls and histamines.

A major development in recent years has been the growth of Type III induced ailments even as the prevalence of Type I has remained stable. Though no specific data exists on the number of people affected by Type III food allergy, it has been estimated by the British Allergy Foundation that nearly 50% of the population may be affected by one or other variety of delayed Type III problem.

The most common factor for the increasing cases of Type III is the change in the dietary patterns of people, especially in urban centres. There has been a significant increase in consumption of Western style foods. Moreover, genetically modified hybrid wheat which contains more gluten has become a larger part of everyday consumption. The increased consumption of processed food, a prevalence of fast food culture, a significant rise in environmental pollution levels, higher usage of medications that damage the normal functioning of the gut flora and the gut barrier, and a leaky stomach lining are some other reasons responsible for the rise in Type III cases.


Food allergy diagnosis is a complex process as several similar symptoms may have different causation factors. The process starts with cross-checking of the patient's complete medical history including identification of time period after which the symptoms manifest themselves. The similarity of symptoms makes it necessary that the condition is properly diagnosed. For instance, a healthcare professional can identify whether the indications are for antibody related Type I or Type III food allergy or for enzyme related food intolerance. One simple method to identify them, among the several the healthcare professionals know, is the time period after eating within which the problem is noticed.

Type I food allergies show immediate reactions within a few seconds and generally at most within half an hour, while Type III takes hours if not days to crop up. Intolerances on the other hand exhibit symptoms after 30 minutes within which time the food has reached the intestines. In most instances, the indications of intolerance disappear within four hours, the time within which the digestive tract digests all food. Also, people with Type III are mostly unaware of the foods that are causing the problem while Type I and food intolerance cases are generally aware of which items caused the problem due to the immediate and severe nature of the reactions. Once the nature of the condition is confirmed, doctors generally recommend a skin prick test for Type I problems and a more detailed test that require blood samples for Type III ailments.

Type I Diagnosis

The immediate and sometimes severe nature of this problem means that the checks are kept to a minimal number of items. Also, as the reactions occur near instantaneously after eating, it is quite easy to spot the adverse products. Doctors are also able to diagnose the problem after talking with the patients as the individual is able to easily recollect what they ate before the problem arose. A skin prick test is recommended to identify the specific IgE antibodies. A food challenge test can help if the symptoms are not severe or life threatening.

Type III Diagnosis

Unlike Type I, the diagnosis of Type III allergies is a longer process. The delayed nature of the reactions makes it necessary for doctors to compile a detailed patient history. The healthcare professionals check the dietary plan and nutritional element in the food to understand what the patient generally eats on a regular basis. This helps them determine the probable items that may have led to the chronic condition. The most common type of checks were the food challenge tests that relied on removing the suspected foods from the diet, checking the symptoms and re-introducing them to check any deviation from the pattern when the product had been kept away from the table. Such tests normally take months due to the inherent nature of the symptoms appearing quite some time after the food was consumed.

The IgG related tests are the best way to check for Type III allergies. Though IgG4 examinations are often of not much use for diagnosis, the checks for IgG1 or IgG3 are helpful in determining if the ailment is caused due to those two antibodies.

It must be kept in mind that criticism of IgG tests is often due to the fact that the antibodies are not suitable for diagnosis of Type I allergies or are not directly related to acute symptoms in food challenge analysis. Scientific papers have always dealt with IgG in relation to Type I allergies. Since the IgG mediated tests are only for Type III allergies, we believe the basis for the criticism is not valid.

Moreover, the advancement in medical testing has made it possible to find if a specific IgG antibody is causing the allergy. Since the delayed reactions do not allow for identification of specific items behind the problem, an analysis that checks for a comprehensive list of items is the best way to go. Also, the transformation of daily cuisine from traditional ethnic items to a homogenous world menu makes it essential that people get checked for as many items as possible to find the culprits. Once the results are available, a personalised menu can be created to ensure the problematic eatables are removed and safer nutritional alternatives are opted for. It is important that only tests from certified organisations are used to locate the probable products that may cause the problem. Once these items are identified, a simple food challenge test can help discern which of the shortlisted items are responsible for the ailment.

Case for Type III Food Allergy Testing

There are various ailments that can be traced to the delayed allergic condition. Some include skin problems, gastrointestinal disorders such as Irritable Bowel Syndrome and Crohn's Disease, headaches including migraine, Autism, diabetes, hypertension, depression, rheumatoid arthritis, and obesity, among others. Though some disorders such as dermatitis may also be caused by IgE antibodies, IgG mediated conditions are also quite common. The healthcare professionals should follow their diagnostic process and if after checking for food intolerances or Type I allergies it is found that they are not the reasons for the allergic reactions, a Type III food test should be recommended.


The only effective and immediate treatment for any food allergy is discontinuing the consumption of the suspected eatables. The nature of the reactions, whether acute or mild or for short periods or longer timelines, are the most important factors to discern what treatment needs to be given. For instance, severe Type I allergies require anti-histamine treatment to maintain homeostasis. IgE mediated ailments may also disappear over a period of time. Children suffering from an allergy often outgrow the problem. Nonetheless, patients or parents of children suffering from the problem must keep the prescribed medications handy for emergency situations.

Type III allergies have no direct medication-based treatment. Once the food items that are causing the disease are identified, their removal helps the body to heal itself over a period of time. Doctors may prescribe medications to help ease any discomfort felt by the patients.


The immediate, acute and in some cases life threatening nature of Type I allergies necessitate that they be handled by specialist doctors at all times. The treatment varies according to the individual and only trained physicians or specialists should handle such cases. Type III allergies are chronic but mild. As such, doctors can easily diagnose and treat the condition. Treatment includes elimination of problem-causing foods from the diet and a course of medication to take care of any uneasiness felt by the patients. Also, the treatment period will be longer as the disease can only be controlled in the long term by removing some items from the diet. Experts treating the condition should have extensive knowledge of food items and their nutrition. They should also be aware of safe alternatives that can be included in the daily menu instead of the products causing the ailment.

Final Word

Type I and Type III food allergies have different physiological attributes and treatment processes. Each is mediated by a different antibody and causes reactions that are specific to the problem and the individual suffering from the problem. IgE and IgG4 cause Type I problems while IgG results in Type III conditions.

Type III allergies cause inflammation of sensitised tissues and continual attack on the same tissue over a period of time results in chronic ailments. It has been shown through various research and scientific papers that proper testing which ascertains if the problem is caused by IgG antibodies is a prerequisite to effective diagnosis and treatment of Type III allergies. The tests have yielded results that have helped to change the food pattern of the affected persons and enabled them to live healthier lives.

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